Digitized by Kansas Correctional Industries

The brine shrimp, Artemia, was used as an experimental organism to study the effects of ⁶⁰Co gamma irradiation on the reproductive performance of an animal population. The total reproductive ability of the brine shrimp was fractionated into various components and the effects of irradiation on each of these components was then determined by studies of reproductive behavior in individual pair matings. In this study, the components identified were the number of broods produced per pair, the number of nauplii voided per pair, the number of nauplii voided per brood, the survival of nauplii to sexual maturity, the number of mature adults produced per brood, and finally the number of mature adults produced per pair. All component parameters of total reproductive performance were shown to be affected by irradiation. However, the number of broods per pair was shown to be the factor most affected by doses of 1200 rads or less. The final parameter, the number of mature adults produced per pair, is really the measurement of the net reproductive potential of Artemia. The net reproduction was also examined by making counts of the total population contained in three liter population cultures, and contrasted to the results obtained with the pair mating studies. It was demonstrated that the population cultures may be maintained by using only a small part of the reproductive potential exhibited in the pair matings. Therefore, we find that the results of pair matings must necessarily be used to assess the amount that the reproductive potential of Artemia is decreased due to various doses of irradiation. It was determined that for Artemia irradiated at the most sensitive stage, a dose of 2100 rads produced sterility. At less sensitive stages, more than 3000 rads would be required to produce sterility. In a single experiment, Artemia irradiated with 300 rads gave an indication of a slight enhancement of reproductive ability as compared to the control animals. In all cases, doses of 600 rads or less showed little effect on the reproductive ability of this species. / Graduation date: 1968

published_or_final_version / Community Medicine / Master / Master of Public Health

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The classical paradigm of radiation biology is based on the notion that ionizing particle has to traverse a nucleus of a living cell in order to damage genetic material either directly or via production of short living free radicals. After DNA damage is introduced it can be either safely repaired and the cell can continue divisions unaltered; or it can result in a failure to repair and cells death; or finally, upon misrepair, the cell would be carrying genetic alteration that could result in cancer or developmental abnormality. Therefore modern risk estimations are based on the notion that nucleus is the true target of radiation effects and those are essentially stochastic with linear dependence on the dose. During the last two decades or so, a different idea was developed based on the observation that irradiated cells can communicate radiation induced stress signals to their unaffected neighbors and themselves become reprogrammed to maintained abnormal radiation-induced phenotype across multiple cellular divisions. Even more astonishingly this phenotype maybe transmitted by irradiated germ cells to unexposed progeny. Here we suggest that these non-targeted effects are maintained by epigenetic mechanisms and examine epigenetic underpinnings of bystander and transgenerational effects in vivo. / xi, 190 leaves ; 28 cm

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Structural aberrations induced in chromosomes by irradiation have been described and classified in great detail (Bender, 1969; Arena, 1971). According to Bender (1969), these aberrations appear after exposure to ionizing irradiation following cell division, or persist unmodified and unrecognizable in interphase cells for many years. In either case, these aberrations persist and can be seen years after radiation exposure.